Check out this thread.

 http://talk.newagtalk.com/forums/thread-view.asp?tid=25254&posts=13&highlight=tile%20&highlightmode=1#M170949

I posted some pictures in it explaining the plastic to clay adapters, plastic to plastic couplers, and just making a tight joint and cementing. I like to cut my plastic a little long so you have to compress it slightly it makes for a nice tight fit and keeps the adapters pushed in to the clay tile if that is the route you are going. It's hard to do this when only replacing one tile so sometimes you need to remove several. It also gets harder to compress when you get into the bigger sizes.